My Acer x263w displays "No Signal" right in the middle of the screen, unmoving too, when my Win 7 x64 PC is asleep. It is connected to an ATI 5450 chipset video card via HDMI. I have 2 other monitors ...

Essentially, a DisplayPort is a digital display interface primarily used to connect a video source to a display device (mostly monitors). It also carries other forms of data such as audio, USB, etc.